Sounding balloon and target assembly



Nov. 1, 1966 L. E. WOOD SOUNDING BALLOON AND TARGET ASSEMBLY Filed NOV.13, 1963 INVENTOR FIG.2

LOUVAN E. WOOD ATTORNEYS United States Patent 3 283 328 SOUNDINGnALLooisi A1 11) TARGET ASSEMBLY Louvan E. Wood, Glenarrn, Md., assignorto The Bendix Corporation, Baltimore, Md., a corporation of DelawareFiled Nov. 13, 1963, Ser. No. 323,528 3 Claims. (Cl. 343-706) Thisinvention relates to a balloon with an insertable collapsible radarreflector and more particularly to a sounding balloon and cornerreflector assembly for use in making winds aloft observations by radar.

The advantages of enclosing a radar reflector within a sounding balloonhave been recounted heretofore. Reference may be made to United StatesPatent No. 2,463,- 517 for a full description of these advantages. Inbrief, they include a marked reduction in the aerodynamic drag of theascending structure and protection from inclement weather conditionswhich may reduce the attainable height of the balloon. The referencedpatent describes a structure comprising gussets of conductively coatedfabric or similar flexible material attached at various points on theinterior of a balloon. It is intended that inflation of the balloon willcause the gussets to be stretched taut to provide a polyhedral cornerreflector.

Attachment of the reflector to points on the interior of the balloontends to limit the expansion of the balloon or to cause a distortion inits shape which destroys the ideal angular relationship of the planes ofthe reflector. Similarly, a distortion of the balloon shape resultingfrom aerodynamic forces causes a distort-ion in the shape of thereflector.

It is an object of this invention to provide a corner reflectorcontained within an expansible sounding balloon and which will maintainits configuration despite changes in shape of the balloon.

Another object of the invention is to provide a collapsible radarreflector which may be inserted in any balloon of appropriate size,thereby permitting salvage of assemblies in which the balloon has becomedamaged prior to use.

A further object is to increase the stability of the radar reflector asit is borne aloft by the balloon thereby providing signal reflections ofincreased strength.

Other objects of the invention will become obvious from study of thefollowing detailed description and the accompanying drawings.

Briefly, the invention comprises a foldable framework supportingflexible gussets of reflective material. This assembly is inserted inthe neck of a deflated balloon. Upon inflation, spring loaded arms ofthe framework expand to support the reflector in a configuration whichis not influenced by the balloon shape. While a simple tet rahedralreflector is described, the principles can be extended to includeoctahedral reflectors, as well as other possible forms.

In the drawings:

FIG. 1 is a perspective view of the reflector in an erected positionwithin an inflated balloon;

FIG. 2 is a detailed view of the hinge portion of the reflector frame;

FIG. 3 illustrates a storage container, portions of which have beenbroken away to reveal the collapsed reflector and balloon containedtherein; and

FIG. 4 illustrates a modification of the radar reflector frame.

Referring to FIG. 1, there is shown a perspective view of the radarreflector in a fully erected position within the inflated balloon 12.Four equal length arms 14 are hinged to a central supporting mast 16.The arms 14 are in cruciform configuration, each being perpendicular to3,283,328 Patented Nov. 1, 1966 mast 16 and to one another. Fourtriangular gussets 18 of reflective flexible material are secured alongtheir equal length edges to arms 14. Alternatively, a single squarepiece of material pierced at the center to allow passage of mast 16 maybe substituted for the gussets 18. Depending from arms 14 and secured tomast 16 along adjacent edges are four additional triangular gussets 18'of flexible, reflective material. It is necessary that the gussets 18'be conductively coated on both sides. Although it is preferred that thegussets 18 also be reflectively coated on both sides, it is essentialonly that the undersides thereof be reflective.

Elastic cords 20 extend from the top of mast 16 to the outer ends ofarms 14. Springs may obviously be substituted for the cords 20. Thetension in cords 20 is sufficient to maintain the arms 14 in an erectedcondition. The cords are sufliciently elastic to permit the arms 14 tobe folded downwardly for storing the reflector and deflated balloon, asshown in FIG. 3. Upon inflation of the balloon the cords retract toraise the reflector to the fully erected position of FIG. 1. Since thecords 20 possess a low mechanical advantage when the arms are foldedparallel to the mast, it may be desirable in certain instances to assistthe opening of the reflector by springs 22, seen in FIG. 2. FIG. 2illustrates also a cruciform hinge 23 by which the arms 14 are ecured tothe mast 16. Again referring to FIG. 1, the ends of the reflectorframework are covered 'by smooth caps 28 which prevent any sharp pointsfrom touching the balloon. The mast 16 is secured at its lower end to anenlarged cylindrical member 30. The reflector assembly is passed intothe balloon and fastened at the neck thereof by means of a clamp 36encircling the member 30. This latter is the only point of attachment ofthe reflector to the balloon. Hence, the balloon is free to expand aspressure conditions may require. Member 30 includes a check valve (notshown) and suitable passages (not shown) to permit inflation of theballoon with buoyant gas. It is clear that the foregoing constructionmakes it possible to assemble the unit in the field just prior toinflation of the balloon. Thus balloons and reflectors may be shippedseparately or serviceable balloons may be substituted for damagedballoons in preassembled combinations.

A suitable means for the storage and handling of the reflector unit andballoon in the collapsed condition is shown in FIG. 3. The balloon 12 iswrapped around the collapsed reflector 10 in a manner to inhibitopening. The entire assembly is then placed inside a tubular container38 which retains the reflector in a collapsed condition and protects theballoon during handling. From FIGS. 1 and 3 it is evident that the sizeof reflector which can be inserted in a balloon is limited by theportion of mast 16 which extends above the arms 14.

Referring to FIG. 4, an alternative embodiment of the inventionemploying a two piece telescoping central mast 16' is shown. Thimodification provides an assembly whose overall length is just slightlylonger than the short side of the reflector, i.e., arm 14, thuspermitting the use of a larger reflector in a given size balloon. Thehollow lower portion 40 of mast 16' slidingly receives an upper portion42. A compression spring 44, secured at its lower end within mastsection 40 bears against the lower end of mast section 42 urging thatsection upwards. Hinge block 23 is attached to mast 40 and the tubulararms 14 are pivotally attached as previously described with reference toFIG. 2.

In the embodiment of FIG. 4 the elastic cords 20 (FIG. 2) are replacedby a non-elastic cord. When the unit is collapsed, arms 14 are foldedparallel to mast 40, and the mast 42 is drawn into mast 40 compressingspring 44.

a As the balloon is inflated, spring 44 expands causing mast 42 to riseand hold arms 14 in their fully erect position.

It should be noted that the aerodynamic drag of separate reflector unitsis reduced by the structure of the invention. The expansion of theballoon and hence attainable altitude is not limited by the reflectorconnection means. Since the center of gravity is below the center ofbuoyancy, a stabilizing moment exists which tends to maintain mast 16vertical and hence the reflector presents a stable orientation to thetracking radar.

It should be understood that this invention, in its broader aspects, isnot limited to the specific embodiment herein illustrated and described,and that the following claims are intended to cover all changes andmodifications that do not depart from the true spirit and scope of theinvention.

The invention claimed is:

1. A sounding balloon and microwave reflector combination comprising anexpansible balloon composed of material transparent to microwaves, andincluding a neck portion for inflation,

a corner reflector of microwaves collapsible for insertion in saidballoon, said reflector including a rigid central mast, a plurality ofrigid arms hinged to said mast to permit folding said arms parallel tosaid mast and a plurality of gussets of flexible, microwave reflectivematerial suspended from said arms and said i mast so as to form aplurality of intersecting plane surfaces upon extension of said armsfrom said mast, means for extending said arms from said mast to maintainthe planes of said gussets in a fixed configuration, and

means securing said reflector central mast to the neck of said balloon.

2. The combination of claim 1, wherein said means for extending saidarms comprises elastic members extending from said mast to the ends ofsaid arms remote from said mast.

3. The combination of claim 1, wherein said means for extending saidarms comprises a telescoping portion of said mast,

means urging said portion for longitudinal extension of said mast, and

linkages from said portion to said arms.

References Cited by the Examiner HERMAN KARL SAALBACH, Primary Examiner.

C. BARAFF, Assistant Examiner.

1. A SOUNDING BALLOON AND MICROWAVE REFLECTOR COMBINATION COMPRISING ANEXPANSIBLE BALLOON COMPOSED OF MATERIAL TRANSPARENT TO MICROWAVES, ANDINCLUDING A NECK PORTION FOR INFLATION, A CORNER REFLECTOR FORMICROWAVES COLLAPISBLE FOR INSERTION IN SAID BALLOON, SAID REFLECTORINCLUDING A RIGID CENTRAL MAST, A PLURALITY OF RIGID ARMS HINGED TO SAIDMAST TO PERMIT FOLDING SAID ARMS PARALLEL TO SAID MAST AND A PLURALITYOF GUSSETS OF FLEXIBLE, MICROWAVE REFLECTIVE MATERIAL SUSPENDED FROMSAID ARMS AND SAID MAST SO AS TO FORM A PLURALITY OF INTERSECTING PLANESURFACES UPON EXTENSION OF SAID ARMS FROM SAID MAST, MEANS FOR EXTENDINGSAID ARMS FROM SAID MAST TO MAINTAIN THE PLANES OF SAID GUSSETS IN AFIXED CONFIGURATION, AND MEANS SECURING SAID REFLECTOR CENTRAL MAST TOTHE NECK OF SAID BALLOON.